Persistence #

In this stage, you’ll add persistence to your key-value store. Data should survive clean shutdowns and be restored when the server restarts.

Clean Shutdown #

When your server receives a SIGTERM signal, it should:

1. Save all key-value pairs to disk
2. Exit gracefully

Startup Recovery #

When your server starts, it should:

1. Check the data directory for existing data
2. Load any previously saved key-value pairs
3. Continue serving requests with the restored data

If no previous data exists, start with an empty store.

Storage #

You can store the data however you choose; the implementation is up to you. Some approaches to consider:

Storage Strategy:

• Snapshot on shutdown: Save all data after receiving SIGTERM
• Continuous persistence: Save changes as they happen

Data Structures:

• Simple formats: JSON & binary serialization, plain text files, etc
• Tree-based: B-trees, Log-structured merge-trees (LSM trees), etc

Your server must accept a --data-dir flag that specifies where to persist data:

$ ./run.sh --port 8080 --data-dir /tmp/tmpzz5vkl5d